Fastening devices for the detachable connecting of objects are known for a long time in the form of bolted connections. Here, a first moveable (separately present) body presently called “fastening body” is connected to a suitable second body presently called “fastening base” by means of rotating relative motion. The second body can be movable (mobile) as well, or it can essentially be stationary (immobile).
The fastening device can have an outer thread (screw). The fastening base has then a suitable inner thread. It can also be moveable (nut) and thus exclusively serve for the fastening. It can however also be arranged within a further object or be part of the same (threaded hole), wherein the other object primarily fulfils other functions (e.g. car body, wall).
The fastening device can have an inner thread (nut). Then, the fastening base has a suitable outer thread. It can also be moveable (screw) and thus exclusively serve for the fastening. It can however also be attached to a further object or be part of the same (threaded bolt, stud bolt), wherein the further object primarily fulfils other functions (e.g. motor block).
A disadvantage of the known fastening devices is that, depending on the length of thread and thread pitch, they need a large number of rotations in order to eventually reach their end position (fastened state), or in order to be fully turned outwards from their counterpiece. For this, an according amount of time is necessary. If further the available space is limited, this time is additionally increased, since a user can turn the according tool (screwdriver, screw wrench) only in small angles, needing to re-apply it again and again.
For this, ratchet spanners and the like are known in the art which allow for a quicker fastening or detaching, or at least for avoiding the repeated applying. Also, driven tools are known. However, all these solutions require at least a single applying of the tool to the screw or nut in order to anchor the same in its fastening ground or to remove the same from it. If several fastening devices must be detached from their fastening bases, the time necessary for this multiplies accordingly.
An improved fastening device is e.g. known from document US 2002/0071738 A1. The same is held in a fastening base by means of mechanical shoulders which are retractable into the body of the fastening device. For detaching the fastening device, a special mechanical tool is necessary; by applying the same to the fastening device, the shoulders are pulled into the inside of the same, or they can be pushed inside, respectively, so that it can be removed from the fastening base.
A further disadvantage lies in the multitude of different engagement geometries (catch profiles). Known geometries are e.g. the slot or the cross recess, internal or external hexagon, or the so called “Torx” (hexalobular socket according to EN ISO 10664). Since connecting devices with different engagement geometries are often used on one component, an according number of different tools must be provided; otherwise, the components can not be assembled or disassembled. The aforementioned fastening device does as well need a tool which is specially provided therefore.
A common problem is the damage of the engagement geometries when screwing, but, at the latest, when unscrewing the fastening device from the fastening base, effected by too high screw-in forces. The usage of torque spanners which are known for a long time (e.g. document U.S. Pat. No. 2,159,354 from the year 1939) has not gained acceptance in all fields of technology, since such a spanner is once again a special tool.
For example, no tool is needed for detaching the fastening device disclosed in document DE 103 13 170 B3; here, loosening of the socket pin is effected by actuating a simple push button.
Also no tool, but electrical power is needed in order to detach the fastening devices shown in document DE 10 2004 004 658 A and US 2005/0172462 A1 from a fastening base. By means of the electrical power, components made of shape memory alloys or bimetal are heated, so that they deform in such a manner that loosening becomes possible.
Another possibility for the detaching of fastening devices is proposed in document DE 19507065 A1. Components which are stable in normal environmental conditions are dissolved by means of a fluid (e.g. water or water vapor), so that then, a pretensioned spring mechanism provides the actual detachment energy which results in a retraction of elements which are anchored form-closing in the fastening base. Also, a (reversible) displacement of the elements by means of mechanical coupling with swellable components is proposed.
The previously mentioned electrically actuatable fastening devices can only produce small forces, so that they can be used only in such situations where the forces necessary for detaching are small. The chemically actuatable fastening means have the disadvantage that they are either actuatable only once, or that they have at least very long switching times.
A further disadvantage lies in the known fact that after a certain time, once assembled connecting means can become hardly, or not at all, be detachable. This can e.g. be effected by slow-acting corrosion. This problem is addressed, with limited success, by means of according coatings.
Another problem comes up in particular when using groups of fastening devices which serve for the common connection of two or several components (e.g. wing of the vehicle, cover panel on a wall). The time which is necessary for detaching the components grows linear with the number of fastening devices, which for large numbers results in very long times. Known solutions with elastic anchors (e.g. plastic clips) do save time during fastening; however, they are so much harder, and not in parallel, to detach. One possibility for the decrease of the time necessary for detaching lies in the usage of electrically or fluidically actuatable fastening means (see above), wherein the limitation to cases of small detachment forces or slow switching times does still exist.
A solution which is also based on a fluidically actuatable drive is shown in document DE 4214206 A1. Here, a working cylinder which acts against disk springs is moved by means of a fluid (e.g. hydraulic oil), with a ball joint bolt being attached thereto in axial direction. The same presses in a resting position with a force which is determined by the disk springs against a rail which is to be fixed. For detaching, the working cylinder is pressurized, such that the bolt detaches from the rail, releasing it. Disadvantageous in this solution is the unchangeable clamping force which is determined by the disk springs, as well as the necessity of being able to build up a pressure by means of the working cylinder that must exceed the holding pressure of the disk springs.